Method of polymerizing fluoroalkyl-substituted cyclotrisiloxanes



United States Patent Oflice 3E,lZZ,5 Zl Patented Feb. 25, 1954 3 122.521Mart-ion on roam immense FLUonoALnYL- SUBSHTUTED CYKILGTRESILQXANES(Bgden R. Pierce, Midland, Mich, assignor to Dow Corning Corporntinn,Midland, Mich, a corporation of Michigan No Drawing. Filed Mar. 18,1950, Ser. No. 15,813 6 Claims. (Cl. 26046.5)

This invention relates to the use of .d-alkaii metal substitutedcarboxylic acid esters as catalysts for the polymerization offiuoroalkyl organocyclotrisiloxanes.

The preparation of polymers composed of units of the formula RCHzCEhSiOin which each R is a perfluoroalkyl radical of from 1 to 10 carbon atomsand each R is a methyl or vinyl radical and up to 10 mol percent unitsof the formula R"" SiO in which each R"" is a methyl, phenyl or vinylradical was achieved by heating the respective homopolymericcyclotrisiloxanes in contact with alkali metal hydroxides, quaternaryammonium hydroxides and organosilicon salts of these hydroxides asdescribed in copending application Serial No. 808,952, filed April 27,1959, by Oscar Johannson. This invention is intended to provide asimilar method employing a new class of catalysts.

This invention relates to a method which comprises heatingcyclotrisiloxanes of the formula RI (RCHzCHzSiOM in which each R is aperfiuoroalkyl radical of from 1 to 10 carbon atoms and each R is aradical selected from the group consisting of the methyl, ethyl andvinyl radicals in contact with a catalyst selected from the groupconsisting of compounds of the formulae R CXCOOX,

n 'ouzhoxrv'ooon'" X-CH(COOR") XCH(COOX) omooon oniooox xonooon'",XonoooX (CHCOOR U and (.CHXCOOX) in which each R" is selected from thegroup consisting of hydrogen and monovalent hydrocarbon radicals of lessthan seven carbon atoms, each R" is an alkyl radical of less than sixcarbon atoms and each X is an alkali metal atom, said catalyst beingpresent in an amount such that there is from 0.5 to 1000 alkali metalatoms alpha to a carbonyl group per 100,000 silicon atoms, at atemperature and for a time suflicient to cause polymerization of thecyclotrisiloxanes to the desired polymer without causing appreciabledegradation of the polymer so formed.

The method described in the above-identified Johannson application takesadvantage of the fact that the cyclic trimers in the presence of theclaimed catalysts open and polymerize to high linear polymers at a ratesubstantially faster than that at which the linear polymers break downto cyclic polysiloxanes .of at least four siloxane units. The method ofthe instant invention likewise takes advantage of these phenomena. Theoptimum temperature and time for any particular cyclotrisiloxane must bedetermined for each system. In general, the more rapid thepolymerization of the cyclic trisiloxane the lower the temperature andthe shorter the time necessary to give the desired high polymer. If theoptimum temperature for a very reactive siloxane is grossly exceeded,the rate of depolymerization will be so great the siloxane may bepolymerized and degraded all in a matter of a few minutes. Furthermore,if the optimum time at any particular temperature is grossly exceeded,the polymer formed will be degraded to cyclics.

In general the polymerization of the cyclosiloxanes of this inventioncan be carried out at temperatures ranging from 30 C. to 250 C. orhigher for times varying from 5 minutes to 3 days.

Another factor which aifects the rate of the reaction is the alkalinityof the catalyst. For any given cyclic siloxane more rapid polymerizationtakes place under given conditions of temperature with a more alkalinecatalyst. Thus the higher the temperature and the stronger the catalystthe more rapid will 'be the polymerization. The lower the temperatureand the weaker the catalyst the longer the polymerization will take.

The cyclotrisiloxanes which are within the scope of this inventioninclude any cyclotrisiloxane in which R is methyl, ethyl or vinyl and inwhich R is any perfluoroalkyl radical of from 1 to 10 carbon atoms suchas 053, C2F5, C3'F7, C7F15 and (11 3821. These perfiuoroalkyl radicalscan be either straight or branched chain radicals. Thus it can be seenthat specific examples of cyclotrisiloxanes within the scope of thisinvention are CH3 (CmFnCHiCHzSiO) 3 It should be understood that any ofthe above cyclosiloxanes can be polymerized either alone to givehomopolymers or two or more of the cyclosiloxanes can be copolymerizedto give copolymers.

The fiuorinated alkyl cyclic siloxanes employed in the method of thisinvention are best prepared by the methods described in the copendingapplication of Ogden R. Pierce and George W. Holbrook, Serial No.594,108, filed June 27, 1956, now U.S. Patent 2,972,519. Briefly thecyclic siloxanes may be prepared by the series of steps of reactingolefins of the formula RCH=CH with silanes of the formula RSiHCl in thepresence of a platinum catalyst under conventional conditions andthereafter hydrolyzinlg the adduct to a siloxane and then heating thesiloxane in the presence of an alkali metal hydroxide under conditionscausing the cyclotrisiloxanes of this invention to distill from thereaction vessel.

An alternative method involves reacting compounds of the formula RCH CHBr with magnesium in diethylether under conventional conditions to givethe corresponding Grignard reagent which can then be coupled withsilanes of the formula R'SiX where X is a halogen atom or an ,alkoxygroup. This method is particularly advantageous where R is the vinylradical. The resulting chlorosilanes or alkoxysilanes are hydrolyzed andcracked to the cyclic trisiloxane as above indicated.

If desired, the cyclotrisiloxanes of this invention can be copolymerizedwith up to 10 mol percent cyclosiloxanes of the formula (R" SiO) inwhich R" is the methyl, phenyl or vinyl radical as is shown in thecopending application Serial No. 594,113, filed June 27, 1956, by EricD. Brown and entitled Low Swell High Temperature Organosiloxane Rubbers.Thus, for example, the cyclotrisiloxanes of this invention can becopolymerized with limited amounts of hexamethylcyclotrisiloxane,trimethyltrivinylcyclotrisiloxane, monovinylpentamethylcyclotrisiloxane,triphenyltrimethylcyclotrisiloxane, or hexaphenylcyclotrisiloxane. Thepreparation of such copolymers containing up to 10 mol percent of R" SiOunits is considered to be within the scope of this invention.

The catalysts employed in the method of this invention are esters andsalts of certain carboxylic acids. These carboxylic acids contain acarbon atom alpha to, Le. attached directly to, at least one carbonylcarbon. At least one of said alpha carbon atoms in any molecule ofcatalyst has an alkali metal atom attached thereto. An alkali metal atomattached to one of these alpha carbon atoms is referred to as an alphaalkali metal atom.

More specifically, the catalysts employed in this invention arecompounds of the formulae R" CXCOOX,

I XCHOHzOOOlV'f COOX XCHCHzCOOX (CHXCOOR"') and (CHXCOOX) in which eachR" is hydrogen or a monovalent hydrocarbon radical, each R is an alkylradical of less than six carbon atoms and each X is an alkali metalatom. For example, each R" can be hydrogen, an alkyl radical such as themethyl, ethyl, isopropyl, t-butyl, isoamyl or n-hexyl radical, analkenyl radical such as the vinyl, allyl or butadienyl radical, acycloaliphatic radical such as the cyclohexenyl or cyclopentyl radicalor the phenyl radical. Each R'" can be, for example, the methyl, ethyl,isopropyl, t-butyl or amyl radical. Each X can be, for example, a sodiumatom, a potassium atom, a lithium atom or a like alkali metal atom.

Typical catalysts for the method of this invention include, for example,such materials as NaCH COONa, KC(CH (C H )COOK,

Na Li @cncoom, C CHOOOL1 a CHaOH (CH3) CHzCHaOHG OK, CH1=GHCHC O ONaCHsCHz iCHsl CO ONa. KCH (COOC H NaCH(COOC H N3 1 I NaC4H900CCHCHzCOOC4H9, CH (C Z)4CHCHCOONB N8 [I N3 NaOOCOHCHaGOONa,CHaCCHCOOCzHs H omomo 0 (CH3) 0 o 0 CH:

.a stoichiometric amount of an alkali metal amide at a temperaturebetween about 170 and 250 C. in a system flushed with nitrogen as shownin US. Patent 2,918,494, Production of Organometallic Compounds, issuedDecember 22, 1959. The alpha alkali metal derivatives of acetoaceticester and the like are best prepared by the reaction of an alkali metal,e.g. sodium, or alkali metal amide, e.g. sodium amide, with a suitablecarboxylic acid ester. The alpha alkali metal derivatives of malonicester and the like are best prepared by the reaction of the ester withan alkali metal alkoxide, e.g. sodium ethoxide. These last two reactionsare illustrated in The Chemistry of Organic Compounds, by Conant andBlatt, 4th ed., The MacMillan Company (1952), pages 259 to 271 at pages266 to 269. The alpha alkali metal derivatives of the alkali metal saltsof malonic acid and the like are best prepared by reacting the salt withthe desired alkali metal amide by the method described in theabove-named patent. Preparations are simplified when all the R' radicalsare identical in a given catalytic compound and all X atoms areidentical in a given catalytic compound.

The amount of catalyst employed is not critical and may range from 1alpha alkali metal atom per 100 silicon atoms to 1 alpha alkali metalatom per 200,000 silicon atoms or from 0.5 to 1000 alpha alkali metalatoms per 100,000 silicon atoms.

If desired, the polymerizations of this invention can be carried out inthe presence of limited amounts of solvent. This is an unexpected resultsince it has heretofore been shown that ordinarily the presence ofsolvents tends to reduce the molecular weight of the polymers obtainedduring alkaline polymerization. One exceptionto this is thenitrogen-containing solvents shown in US. Patent 2,634,284. With thematerials of this invention, however, high polymers can be obtained evenin the presence of hydrocarbon solvents such as toluene, xylene and thelike or ethers such as dibutylether.

The process of this invention is particularly suitable for preparingrubber grade base polymers of the type disclosed and claimed in theaforesaid copending Brown application. Such rubbers as shown in theBrown case combine exceptionally low swell in aromatic solvents withexcellent thermal stability and excellent stress strain properties.Furthermore, the method of this invention imparts to the Brown rubbersthrough the polymers produced a notable improvement in tear strength aswell as occasional improvement in tensile strength over rubbers preparedfrom polymers polymerized with other catalysts.

The following examples are illustrative only and are not to be construedas limiting the invention which is properly delineated in the appendedclaims. All proportions not otherwise defined are described in parts byweight.

EXAMPLE 1 78 grams (0.5 mol) of [CF CH CH Si(CH )O] and 0.0172 gram(0.002 mol) of [(CH )(C H )SiO] were mixed and heated to 150 C. 0.0073grams of a-SOdiO sodium acetate (equivalent to one oc-SOdillIIl per10,000 silicon atoms) Was added to the mixture and the resulting systemwas heated at 150 C. for one hour producing a copolymer A of about 0.4mol percent methylvinylsiloxane units and 99.6 mol percent3,3,3-trifiuoropropylmethylsiloxane units, said copolymer having aWilliams plasticity of about 0.250 inch.

parts by weight of copolymer A were incorporated into a standard rubberstock formulation by milling with 20 parts of a fume silica, 10 parts ofa silica xerogel, 5 parts of a hydroxy-endblocked dimethylpolysiloxanecontaining 3.7 percent silicon-bonded hydroxyl groups, 1 part of ferricoxide and 1 part of benzoyl peroxide. The resulting stock waspress-molded and vulcanized for 5 minutes at C. and 5000 p.s.i. andsamples were then oven-cured for 24 hours at and 250 C. respectively.The durometer D, tensile strength T (p.s.i.) and percent elongation atbreak B were measured.

183.4 grams (1.24 moles) of [CF CH CH Si(CH )O] and 0.602 gram (0.007mol) of [(CH )(C H )SiO] were mixed and heated to 150 C. To this mixturewas added 0.002 gram of a-sodio sodium acetate (equivalent to onea-sodium per 80,000 silicon atoms). The resulting mixture was heated for4 hours at 150 C. pro ducing a copolymer B of 0.56 mol percentmethylvinylsiloxane units and 99.44 mol percent 3,3,3-trifluoropropylareasai methylsiloxane units, said copolymer having 9. Williamsplasticity of about 0.250 inch.

Copolytner B was substituted for the polymer of Example l in the rubberstock formulation described therein. The resulting rubber had about thesame physical properties as those shown in Table 1.

EXAMPLE 3 140.5 grams (0.894 mol) of [CF ClI CI-I Si-(CH )O] and 0.344gram (0.004 mol) of [(CH )(C H )SiO] were mixed and heated to 150 C. Tothis mixture was added 0.0197 gram of a-sodio sodium acetate (equivalentto one a-sodiurn per 5000 silicon atoms), and the mixture was heated for1 hour at 150 C. The resulting product was a copolymer C of 0.446 molpercent methylvinylsiloxane units and 99.554 mol percent3,3,3-trifluoropropylmetnylsiloxane units, said copolymer having aWilliams plasticity of about 0.250 inch.

100 parts by weight of copolymer C were mixed with 30 parts of a fumesilica, 15 parts of a silicaxerogel, parts of a hydroxy endblocked 3,3,3trifiuoropropylmethylpolysiloxane fiuid containing 1.56 percent byweight silicon-bonded hydroxyl groups, 0.28 part of TiO and 1 part ofbis-2,4-dichlorobenzoyl peroxide. formulation was vulcanized for 5minutes at 125 C. at 2000 psi. and oven-cured for 8 hours at 200 C. Thedurometer D, tensile strength '1 (p.s.i.), percent elongation at break Eand tear strength (pounds per inch) were measured and compared with acommercial stock.

Table II Polymer D T E Tear 71 1, 405 235 117 Commercial 62 l, 09 203 70EXAMPLE 4 are substituted for the cyclic mixture in Example 3, theresulting products are respectively a3,3,3-trifluoropropylmethylpolysiloxane stiff gum and a3,3,4,4,5,5,5-heptafluoropentylmethylpolysiloxane stilt gum, each gumproducing similar excellent rubbers when employed in the rubber stockformulation in Example 3.

EXAME'LE 5 When a mixture of [CF CH CH SKCHQO] [CF CH CH SKC HQO] 3EXAMPLE 6 When K Li CHZ=CHCHCOOK, CHCOOLl and (NaCHCOONa) are eachsubstituted in a ratio of 0.5 mol per mol of NaCl-l COONa in Example 3,similar gum copolymers are produced. When each of these gum copolymersis employed in the rubber stock formulation in Example 3, similarexcellent rubbers result.

EXAMPLE 7 75 grams (0.480 mol) of [CF CH CH Si(CH )O] and 0.172 gram(0.002 mol) of [(CH )(C H )SiO] This were mixed and heated to 61 C.NaCH(COOC H was prepared by adding sodium to a solution of malonic esterin the dimethyl ether of ethylene glycol such that there was 1 gram molof a-sodium per 1390 grams of solution. 0.1343 gram of this oz-SOdiOdiethylmalonate solution (equivalent to one tut-sodium per 5,000 siliconatoms) was added tothe cyclic mixture which was then heated for one hourat about 61 C. The product was a copolymer D of 0.415 mol percentmethylvinylsiloxane units and 99.585 mol percent3,3,3-triflu0ropropylmethylsiloxane units, said copolymer having aWilliams plasticity of about 0.070 inch.

Copolymer D was substituted for copolymer C in the rubber stockformulation employed in Example 3. After the same vulcanization andcurethe durometer, tensile strength, percent elongation at break andtear strength were measured.

Table III :D T E Tear EXAMPLE 8 When I! K C O 0 CH3 CHaC CH0 0 004E!)and NaOHCBfiO 0 0 CH3 are each substituted mol for mol for theNaCH(C-OOC H 2 would cxrwo 0 on'" XCH[COOR'] XCH[COOX] omoooa omoooxXCHC 0 OR', xono o ox (CHXCOOR') and (CHXCOOXh, in which each R isselected from the group consisting of hydrogen and monovalenthydrocarbon radicals of less than seven carbon atoms, each R is an alkylradical of less than six carbon atoms and each X is an alkali metalatom, said catalyst being present in an amount such that there are from0.5 to 1000 alkali metal atoms alpha to a carbonyl group per 100,000silicon atoms, at a temperature and for a time sufiicient to causepolymerization of the cyclotrisiloxanes to the desired polymer withoutcausing appreciable degradation of the polymer so formed.

2. A method which comprises heating a mixture of (1) cyclotrisiloxanesof the formula (RCHzCHgiO): in which each R is a perfiuoroalkyl radicalof from 1 to 10 carbon atoms and each R is a radical selected from thegroup consisting of the methyl, ethyl and vinyl radicals and (2)cyclotrisiloxanes of the formula (R"" SiO) in which each R"" is selectedfrom the group consisting of the methyl, phenyl and vinyl radicals, (2)being present in an amount up to 10 mol percent of the mixture, in

contact with a catalyst selected from the group consisting of compoundsof the formulae R" CXCOOX,

lv'omgoxrv'coon'" XCH[COOR"'] XCH[COOX] CHiOOOR' CHZCOOX Xt JHoooR'"XCHG 0 0X (CHXCO0R"') and (CHXCOOX) in which each R" is selected fromthe group consisting of hydrogen and monovalent hydrocarbon radicals ofless than seven carbon atoms, each R' is an alkyl radical of less thansix carbon atoms and each X is an alkali metal atom, said catalyst beingpresent in an amount such that there are from 0.5 to 1000 alkali metalatoms alpha to a carbonyl group per 100,000 silicon atoms, at atemperature and for a time suflicient to cause polymerization of thecyclotrisiloxanes to the desired polymer Without causing appreciabledegradation of the polymer so formed.

3. The method in accordance with claim 1 wherein R is a methyl radicaland the catalyst is Ot-SOdiO sodium acetate.

4. The method in accordance with claim 1 wherein the cyclotrisiloxane is[CF CH CH Si(CH )O] and the catalyst is a-sodio sodium acetate.

5. The method in accordance with claim 2 wherein cyclotrisiloxane (1) is[CF CH CH Si(CH )O]- cyclotrisiloxane' (2) is [(CH (C H )SiO] and thecatalyst is a-sodio sodium acetate.

6. The method in accordance with claim 2 wherein cyclotrisiloxane (l) is[CF CH CH Si(CI-l )O] cyclotrisiloxane (2) is [(CH (C H )SiO] and thecatalyst is NaCH(COOC H References Cited in the file of this patentUNITED STATES PATENTS Closson et a1. Dec. 12, 1959 Pierce et al Nov. 22,1960 OTHER REFERENCES PATENT QFFICE RRECTIQN February 25, 1964 UNITEDSTATES CERTIFICATE OF QG Patent No. 3,122,521

Ogden R. Pierce s in the above numbered patead as rtified that errorappear tters Patent should r should appear a on of the formula in thepatent:

" read (CHXCOOR') same column for "(CHXCOOR") column 2 line 42 forMRIIIIM d R111 read R SiHCl line 41:5

l line 48, RSiHC1 Signed and sealed this 8th day of December 1964,

(SEAL) Attest: ERNEST W. SWIDER EDWARD J. BRENNER Commissioner ofPatents nesting Officer

2. A METHOD WHICH COMPRISES HEATING A MIXTURE OF (1) CYCLOTRISILOXANESOF THE FORMULA